A hybrid powertrain or driveline may include a belt integrated starter/generator (BISG) to charge a battery of a vehicle, provide propulsion power to the vehicle, and to start an engine of the vehicle. The BISG may be mechanically coupled to an engine crankshaft or camshaft via a belt. A tensioning device may be applied to the belt to keep the belt snugly placed against a crankshaft pulley and a pulley that is coupled to a BISG shaft or a shaft that is coupled to the BISG. However, the pulley may not be effective to transfer torque between the BISG and the engine during some conditions and the belt may slip. The belt may degrade when belt slip is present and energy transfer between the BISG and the engine may be reduced. Therefore, it may be desirable to provide a way of reducing the possibility of belt degradation and maintaining energy transfer between the BISG and the engine during conditions where the possibility of belt slip may increase.
The inventors herein have recognized the above-mentioned issues and have developed a powertrain operating method, comprising: cranking an engine via an integrated starter/generator, a pinion gear, and a flywheel during a first engine start; and cranking the engine via the integrated starter/generator, a belt, and a crankshaft pulley during a second engine start.
By engaging a pinion gear that is coupled to a BISG to an engine flywheel during engine starting, it may be possible to provide the technical result of reducing belt degradation and ensuring energy transfer between a BISG and an engine. In particular, a pinion gear that is coupled to a shaft of the BISG may engage a flywheel that is coupled to the engine so that a gear connection is provided between the BISG and the engine during conditions in which large amounts of energy may be exchanged between the BISG and the engine. The gear connection may reduce the possibility of belt slippage by increasing rigidity between the BISG and the engine. During conditions where energy transfer between the BISG and the engine is at lower levels, the pinion gear may be disengaged from the flywheel to reduce engine noise and vibration. A belt connection between the BISG and the engine may allow efficient torque transfer at reduced noise and vibration levels during conditions where energy transfer between the BISG and the engine is lower.
The present description may provide several advantages. In particular, the approach may allow a BISG to transfer large amounts of energy to an engine without belt degradation. Further, the approach may keep engine noise levels low during conditions when transfer of large amounts of energy between the BISG and the engine is not desired. Further still, the approach may reduce engine starting time when an engine is being cold started.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
FIGS. 3A-3I are drawn approximately to scale.